Lemonade was brought to my attention for the guy I'm doing work for. It's a set of IMAP extensions that make IMAP more suitable for mobile phones and devices. Some of their goals obviously overlap with the work the XMPP/Jabber community has been doing. The most obvious being the extensions to handle streaming multimedia content. Looking through their list of goals in their charter, practically every item seems to be handled one of our RFCs or XEPs already. Perhaps its time for the IETF's left hand to check up on its right hand.
I don't see how XEPs are
I don't see how XEPs are relevant to IMAP or Lemonade or email in general.
Also, the JSF is not an IETF working group, so it's wrong to imply that this is a left-hand/right-hand thing - it's more in the realm of liaison between different standards organizations.
You specifically mention streaming media. The Lemonade extension simply allows an IMAP client to create a self-authenticating IMAP URL to a media atachment. This URL can then be passed to a streaming server so that the client can display the media online without downloading it. The documented protocol for doing this uses SIP, but there's no reason you couldn't write a XEP for the XMPP equivalent.
I see no duplicated work here.